"Our Last Crusade or the Rise of a New World" is set in a world divided by a long-standing war between the scientifically advanced Empire and the mystical Sovereignty. The conflict stems from their opposing ideologies and methods of harnessing power, with the Empire relying on technology and the Sovereignty on astral energy. The story centers on two individuals from opposing sides: Iska, a skilled swordsman and former soldier of the Empire, and Aliceliese "Alice" Lou Nebulis IX, the Sovereignty's most powerful astral mage and heir to the Lou Nebulis family. Iska, once a promising soldier, becomes disillusioned after a failed mission results in the loss of his comrades. He is later tasked with a covert operation to infiltrate the Sovereignty and capture Alice, who is known as the "Ice Calamity Witch" for her devastating ice-based powers. During a chance encounter, Iska and Alice cross paths and engage in a fierce battle, only to be interrupted by external forces. This encounter sparks a mutual curiosity and respect between the two, despite their opposing loyalties. As the story progresses, Iska and Alice continue to cross paths, each time challenging their beliefs and the rigid boundaries of their war-torn world. Their interactions reveal a shared desire for peace and a growing bond that transcends their factions. However, their relationship is complicated by the expectations and pressures of their respective societies, as well as the machinations of powerful figures within both the Empire and the Sovereignty. The narrative explores themes of conflict, loyalty, and the possibility of reconciliation between opposing forces. Supporting characters, such as Rin, Iska's childhood friend and fellow soldier, and Mismis, his commanding officer, provide additional perspectives on the war and its impact on individuals. Meanwhile, Alice's interactions with her subordinates, including her loyal maid Jhin, highlight the internal struggles within the Sovereignty. The series balances action, political intrigue, and character development, with battles showcasing the unique abilities of astral mages and the technological prowess of the Empire. The evolving dynamic between Iska and Alice serves as the emotional core of the story, offering a glimpse of hope amidst the chaos of war. The anime adapts the light novel series, presenting a world where the lines between enemies and allies blur, and the potential for a new future emerges through the actions of its protagonists.